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When a reinforced concrete member is put in tension, after cracking, the member elongates by widening of cracks and by formation of new cracks. Figure 1 Formation of internal cracks. Ignoring the small elastic strain in the concrete between the cracks, we can relate the crack width to the strain of the member by:
Large cover depths (50–75 mm) are required to protect reinforcement against corrosion in aggressive environments, but thick cover leads to increased crack widths in flexural reinforced concrete members. Large crack-widths (greater than 0.3 mm) permit ingress of moisture and chemical attack to the concrete, resulting in possible corrosion of ...
Cracks in the concrete can be checked by replacing the yield stress in the utilization tensor by the bar stress at which the maximum crack width occurs. (This bar stress depends also on the bar diameter, the bar spacing and the bar cover.)
Concrete cracks due to tensile stress induced by shrinkage or stresses occurring during setting or use. Various means are used to overcome this. Fiber reinforced concrete uses fine fibers distributed throughout the mix or larger metal or other reinforcement elements to limit the size and extent of cracks. In many large structures, joints or ...
the plastic zone at a crack tip may have a size of the same order of magnitude as the crack size; the size and shape of the plastic zone may change as the applied load is increased and also as the crack length increases. Therefore, a more general theory of crack growth is needed for elastic-plastic materials that can account for:
Knowing that the new structures are deeply inspected before being put in service, the example considers a maximum undetectable crack size as about 1.27 mm (0.05") for a new structure. To simulate the variation of possible initial crack sizes, the Monte Carlo simulation method was used to randomly generate values between the given limits. In ...
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Deflection limits are set to ensure that crack widths in steel-reinforced concrete are controlled to prevent water, air or other aggressive substances reaching the steel and causing corrosion. For FRP-reinforced concrete, aesthetics and possibly water-tightness will be the limiting criteria for crack width control.